The frozen confection which is variously known as frozen custard, soft ice cream, soft serve ice cream and ice milk is generally made in the following manner. A dairy, franchiser or other supplier manufactures a liquid mix and supplies it in bulk or in containers for refrigeration at the confection retailers. As needed, the retailer makes and dispenses the frozen confection, generally using a machine which accepts a supply of the liquid mix, directs the supply to a mixer where air is mixed with the liquid mix and forwards the air/liquid mix, i.e. a foam, through a freezer, to a dispenser. Typically the dispenser is valve-operated to dispense the frozen confection into an edible cone, a dish or another container.
The consistency, both in density and texture, of such frozen confections is substantially affected by the porportion of air to liquid mix provided in the mixture that is subjected to the freezing step.
In the frozen confection trade, the proportion of air mixed in to the liquid is referred to as the "overrun." According to convention, overrun is expressed as a percentage, equal to twice the percentage of air, by volume, in the air/liquid mixture. As an example, an air/liquid mix having a 50 percent overrun includes 33 1/3 percent air and 66 2/3 percent liquid mix, by volume.
Although each freezing machine generally has the percentage overrun for its pump set at a constant value when the machine is first installed, this assumes that the machine will always use the same recipe of liquid mix. However, different recipes can call for different overruns and the seller's conception of what consistency of the public wants in a frozen confection varies from store to store and locality to locality.
For these reasons, manufacturers of the freezing machines and of the pumps therefore desire to provide a means by which one design of pump can by selection or minor servicing provide any of several amounts of overrun.
One problem which must be taken into account is that health regulations in most localities require that all parts of the freezing machine that come in contact with the liquid mix, before, during and after freezing, be disassembled from the machine frequently and thoroughly cleaned.
Accordingly, a good design of pump is one which minimises the need for and facilitates cleaning and permits the desired level of overrun to be maintained during use in spite of frequent disassembly and reassembly of the pump.
The present inventor believes that prior available devices are not fully satisfactory and accordingly has designed what he considers to be an improved mix blending pump.